Advisory, Articles

Burning issues

Compliance with Part G of the Building Regulations aims to highlight the need for hot water safety, sanitation and efficiency. Julie McLean offers advice on the products that can improve safety.

A recent survey by water controls manufacturer Honeywell highlighted a gap in installer knowledge when it comes to thermostatic mixing valves (TMVs). Only 17% of installers knew the difference between TMV products. They play a vital part in hot water safety and ensuring an installation is compliant with Part G of the Building Regulations. Therefore, a better installer understanding of the products that are available to improve safety will help to reduce hot water related injuries.

Improving safety
Water above 44°C can scald, causing the risk of serious injury and even death. TMVs control water temperatures accurately for baths, showers, sinks and bidets. They maintain pre-set temperatures – even if the water pressure varies when other appliances are being used. They offer flexible installation and can be fitted under baths and sinks, as part of shower fittings, or even as a feature of exposed hot and cold water mixers.

The temperature that the hot and cold water entering the valve is mixed to can be set by the installers. If there is a cold water supply failure, the thermostatic mixing mechanism will automatically shut down the flow to prevent discharge of dangerously hot water. The flow will also be shut down in the event of a hot water supply failure, to prevent thermal shock. In the event of a sudden temperature increase from the supply, the TMV will quickly adapt to deliver water at a safe temperature.

All TMVs protect against hot-water scalding. However, TMV2-approved and TMV3- approved valves are suitable for separate applications. TMV2-approval identifies valves suitable to prevent domestic scalding. It certifies that the valves it approves conform to the performance requirements of BS EN 1111 and BS EN 1287. On the other hand, TMV3-approved valves, which offer a higher level of protection, are the only models considered suitable for NHS and healthcare applications.

TMV installation
All new-build and converted-usage homes across England and Wales must incorporate TMVs, but that still leaves plenty of homes that are without them. As with any appliance, it is important to follow the manufacturer’s guidelines. Before installation, it is essential to ensure the valve specification is appropriate – the flow-rates, pressures and water temperatures must be within the manufacturer’s stated limits. They also need to be fitted to allow easy maintenance and service in the future.

The Chartered Institute of Plumbing and Heating Engineering (CIPHE) do not recommend using one TMV to control the temperature of the hot water supply to all the appliances in an enclosed space such as a bathroom. This is because it’s likely that runs of pipework from the TMV to the outlets would exceed the recommended 2 metre limit. Also, guidance gives maximum temperatures for each appliance – for example, 46°C for a bath and 41°C for a basin. If one TMV is used to supply both, either the bath water would be too cold or the water from the taps in the basin too hot.

The TMVA Code of Practice states that the operation of one or more outlets should not affect the operation of any other outlet. The length of the pipe run and the volume of mixed water after the valve should be kept to a minimum when one valve is used to supply mixed water to a number of outlets. The maximum pipe run after the mixing valve should allow the required mixed temperature at the furthest outlet to be reached within 30 seconds.

TMV maintenance
Many areas in the UK have hard water. This, along with the frequency of its use, will determine how often a TMV needs servicing. BEAMA (British Electrotechnical and Allied Manufacturers Association) suggest measuring the mixed water temperature at the outlet by carrying out the cold water supply isolation test by isolating the cold water supply to the TMV, then wait for five seconds.

If water is still flowing, check the temperature is below 46°C. If there is no significant change to the set outlet temperature (2°C or less change from the original settings) and the fail-safe shut-off is functioning, then the valve is working correctly and no further service work is required.

Hot surfaces
Radiators and associated pipework also have the potential to cause burns. They can be covered so the maximum accessible surface temperature does not exceed 43°C. The risk of burns from hot surfaces may be reduced by low surface temperature heat emitters, locating sources of heat out of reach, guarding the heated areas by providing radiator covers, and covering exposed pipework.

Sanitation
In February 2013, the HSE (Health and Safety Executive) banned the use of elemental copper as a biocide. This was a way of controlling Legionella, a potentially fatal form of pneumonia that can be found in water in temperatures between 20°C and 45°C. There are, however, other methods of water treatment biocides which involve silver ionisation and they can treat all water-borne bacteria and viruses.

Hot water storage cylinders can store water at 60°C or more – Legionella bacteria cannot survive at this temperature. As a result of this, stored hot water TMVs should be used as previously mentioned.

Legionella tends to prefer stagnant water. Therefore, to minimise Legionella growth, keep pipework as short and direct as possible, making sure it is adequately insulated. To further reduce risk, outlets – including showerheads and taps – should be flushed out. Identify the outlets furthest and closest to each tank or cylinder and check the distribution temperatures. The hot water storage cylinder temperatures should also be checked regularly – water should be drained to check for debris or signs of corrosion.

Water efficiency
Part G also addresses the possibilities of using a rainwater harvesting system to provide water to any sanitary device. It works by taking the rain from roof gutters, filtering out leaves and debris, and storing the water in an above ground or underground tank.

This water can then be used instead of mains water from the tap for car-washing, garden irrigation, toilet flushing and washing machines. This reduces the amount of mains water we depend on and saves money on water bills. Water butts, rain-traps and fully integrated systems are all available to reduce the volume of water wastage. It can reduce water consumption by up to 50% in domestic installations and up to 85% within commercial applications. This offers installers with a great add-on selling opportunity. Part G also includes greywater systems where water is recycled from baths, showers and sinks, and reused to flush toilets.

Building Regulations are there to promote best practice and safety. In the case of Part G, this is particularly in regard to hot water safety, where scolding and burning tends to affect the most vulnerable – children under the age of five and adults over 65 have thinner skin and are far less tolerant to higher water temperatures. As a result, everyone in the industry should be researching which products can help with Part G compliance.